netdev - Re: [PATCH net v2] net: ag71xx: fix mdio subnode support

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Message-ID: <20191001164340.GC2031@lunn.ch>
Date:   Tue, 1 Oct 2019 18:43:40 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     David Miller <davem@...emloft.net>
Cc:     o.rempel@...gutronix.de, jcliburn@...il.com, chris.snook@...il.com,
        kernel@...gutronix.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net: ag71xx: fix mdio subnode support

On Tue, Oct 01, 2019 at 09:03:20AM -0700, David Miller wrote:
> From: Oleksij Rempel <o.rempel@...gutronix.de>
> Date: Tue,  1 Oct 2019 08:41:47 +0200
> 
> > @@ -571,7 +571,9 @@ static int ag71xx_mdio_probe(struct ag71xx *ag)
> >  		msleep(200);
> >  	}
> >  
> > -	err = of_mdiobus_register(mii_bus, np);
> > +	mnp = of_get_child_by_name(np, "mdio");
> > +	err = of_mdiobus_register(mii_bus, mnp);
> 
> of_get_child_by_name() can fail, so error checking is necessary
> before you pass mnp into of_mdiobus_register().

Hi David

/**
 *	of_get_child_by_name - Find the child node by name for a given parent
 *	@node:	parent node
 *	@name:	child name to look for.
 *
 *      This function looks for child node for given matching name
 *
 *	Returns a node pointer if found, with refcount incremented, use
 *	of_node_put() on it when done.
 *	Returns NULL if node is not found.
 */

So on error, it returns NULL. And passing NULL to
of_mdiobus_register() is the correct thing to do if there is no DT
node. of_node_put() is also O.K. with NULL.

So this is all O.K. as is.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew